Two polymolybdate-directed Zn(II) complexes tuned by a new bis-pyridine-bis-amide ligand with a diphenylketone spacer for efficient ampere sensing and dye adsorption

By introducing a new semi-rigid bis-pyridine-bis-amide ligand with diphenylketone as a spacer, 4,4'-bis(4-pyridinecarboxamide)phenylketone(L), two polymolybdate-based metal-organic complexes (MOCs), namely, [ZnL(MoO4)] (1) and (H2L)(4)[Zn(CrMo6(OH)(6)O-18)(2)(H2O)(4)][ZnL2(CrMo6(OH)(6)O-18)(2)(H2O)(2)]center dot 8H(2)O (2), were successfully assembled via a solvothermal method. Complexes 1 and 2 show different structures by introducing different Anderson-type [TeMo6O24](6-)/[CrMo6(OH)(6)O-18](3-) polyoxoanions in the H2O-EtOH mixture solvent, including the 3D network of 1 and the 0D supramolecular structure of 2. An interesting structural feature in 1 is that an inorganic {ZnMoO4}(n) layer could be formed, although an A-type [TeMo6O24](6-) polyoxoanion was utilized as the raw material. Noteworthily, complexes 1 and 2 can be employed as dual-function electrocatalysts for the electroreduction of Cr(vi), KBrO3, and H2O2 and the electrooxidation of ascorbic acid (AA). They can also be used as electrochemical sensors for the quantitative detection of Cr(vi), KBrO3, H2O2, and AA; in particular, low detection limits (0.033 mu M for 1 and 0.037 mu M for 2) were observed for Cr(vi) ions. Complex 2 shows a rapid and highly selective adsorption activity for the organic dyes crystal violet and methylene blue.

Automated summary

Two new metal-organic complexes have been successfully synthesized using a new semi-rigid bis-pyridine-bis-amide ligand. They exhibit dual-function electrocatalytic and electrochemical sensing properties.